Effect of Halloysite Nanoclay on the Properties of Castor Oil–Based Polyurethane Synthesized by Microwave-Assisted Method

Abstract

Abstract A series of castor oil–based polyurethane (PU) with and without the incorporation of halloysite nanoclay (HNT) were prepared via conventional method using oil bath and with the aid of microwave radiation at varying temperatures. The PUs were characterized by using attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis, X-ray diffractometry, and transmission electron microscopy. The ATR-FTIR spectra of PUs indicated complete polymerization by the disappearance –NCO peak at 2,270 cm−1 with a shorter reaction time of ≈130 min by using microwave-assisted method compared to using conventional method (≈450 min) at the same reaction temperature of 55°C. Compared to pure HNT with d-spacing of ≈6.98 nm, an increment of d-spacing for HNT incorporated PUs synthesized by both conventional and microwave methods indicated the intercalation of PU chains within HNT layers. The sharper diffraction peak of castor oil–based PU with HNT synthesized by conventional method at 2θ = 11.6° compared to microwave-assisted method at 2θ = 11.9° indicated the formation of more crystalline PU nanocomposites by conventional method and modification of the surface morphology occurred with microwave radiation.